The Collaborative International Dictionary of English v.0.48:
Bivalved \Bi"valved\, a. Having two valves, as the oyster and some seed pods; bivalve. [1913 Webster]WordNet (r) 3.0 (2006):
bivalved adj 1: used of mollusks having two shells (as clams etc.) [syn: bivalve, bivalved] [ant: univalve]